Microsoft's typed JavaScript superset. The default language of modern web development; 90%+ of new TS-or-JS projects pick TS in 2026.
From Wikipedia
TypeScript (TS) is a high-level programming language that adds static typing with optional type annotations to JavaScript. It is designed for developing large applications. It transpiles to JavaScript. It is developed by Microsoft as free and open-source software released under an Apache License 2.0.